Mechanism of Aryldestannylation of Alkenylstannanes with Arylpalladium Complexes

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Both ArPd(PPh_3)_2I and ArPd(PPh_3)_2BF_4 aryldestannylated PhCH=CHSnR_3 and Ph(R_3Sn)C=CH_2(R=Bu, Ph)to give PhCH=CHAr and Ph(Ar)C=CH_2, respectively. In the absence of strong neutral ligands such as PPh@_3, however, the counter anion of the palladum complexes showed drastic effect on the reaction profile. Reaction with PhCH=CHSnR_3, [ArPd]^+BF_4^- gave Ph(Ar)C=CH_2, whereas Ar-Pd-I gave PhCH=CHAr.In the presence of coordinatively strong ligands such as PPh_3 or I^-, arylpalladium complexes aryldestannylate alkenylstannanes via transmetallation-reductive elimination mechanism as following scheme.<<chemical formula>>In the absence of coordinatively strong ligands, the reaction with [Ar-Pd]^+BF_4^- proceeds through addition-elimination mechanism as following scheme.<<chemical formula>>In the palladium catalyzed C-C coupling of organic electrophiles with organometallics, organs-palladium species expect to be a key intermediate. Present results exemplify an important role of the ligands of organopalladium intermediates to design reaction pathway.